This invention relates to a system for, and a method of, treating occluded vessels (e.g. an artery) and capturing friable emboli which may break away from the lesion in the vessel during an interventional procedure. The system and method of the present invention are especially useful when performing carotid interventional procedures in order to prevent embolic debris from entering and occluding downstream blood vessels leading to the brain which, if blocked, may cause a stroke. However, the system and method of this invention can be adapted by a person of ordinary skill in the art for use in numerous other vascular interventional procedures.
In recent years, numerous procedures have been adapted for expanding blood vessels (e.g. arteries), at the positions of lesions in the blood vessels, so that blood can flow through the blood vessels without obstruction from the lesions. In the process of expanding such blood vessels at the positions of the lesions, emboli may become detached from the lesions and enter the bloodstream and subsequently migrate through the patient""s vasculature to block blood vessels leading to sensitive organs such as the brain, where they may induce trauma.
Procedures have been adapted in recent years for preventing embolic debris from flowing through the vessels in the direction of the blood flow. For example, filters have been provided for trapping the emboli. When lesions develop in the carotid artery of a patient, the placement of a filter in the patient""s vasculature can somewhat reduce the movement of the emboli to the patient""s brain, thereby preventing strokes from occurring.
Such filters are usually delivered in a collapsed position through the patient""s vasculature and are then expanded once in place to trap the emboli. After emboli have been trapped, the filter is collapsed to remove the filter (with the trapped emboli) from the vessel. However, it is possible for some of the trapped emboli to escape from the filter during the time that the filter is being collapsed and/or removed from the blood vessel. When an interventional procedure is being performed in a carotid artery, even a trace release of emboli can be damaging. For these reasons, attempts to treat lesions in the carotid arteries have been somewhat limited due to the danger presented if all of the embolic debris is not collected during the procedure.
Therefore, in light of the above, it would be desirable to have a system and method which can be utilized to treat an occluded vessel and trap emboli that may be formed during the vascular procedure. Such a system and method also must prevent the emboli from escaping from the filter during the time that the vascular procedure is being performed. Additionally, it also would be advantageous if the filter could remain implanted within the patient""s vasculature, thereby eliminating a potential source for the release of trapped emboli since the filter would not have to be collapsed and removed from the blood vessel. Such a device or method should be easy to use and have minimal or no adverse impact on the patient.
The present invention provides a self-expanding filter having a deployable resilient distal portion with properties of passing fluid (e.g. blood) in a vessel (e.g. an artery) while blocking the passage of emboli released in the fluid. The self-expanding filter is to be disposed within the vessel, in the direction of fluid flow in the vessel, with its resilient proximal and distal ends at positions past the lesion to be treated in the vessel. The distal end of the self-expanding filter is first deployed against the vessel wall, ready to trap any emboli which may be released into the blood stream. A restraining sheath previously has been placed over the self-expanding filter to maintain the filter in a collapsed position. When the distal end of the filter is to be deployed within the vessel, the physician merely retracts the proximal end of the restraining sheath the proper distance to expose only the distal portion of the filter. Since the filter is self-expanding, the distal end expands and contacts the wall of the vessel to form a seal which prevents emboli from escaping. Blood is permitted to pass through the fine openings of the filter while emboli of particular size are trapped by the filter.
An interventional medical device can be placed in the area of the lesion to treat the lesion and expand the vessel. For example, an expandable member (e.g. dilatation balloon) and expandable stent can be positioned within the vessel at the site of the lesion. The expandable member is dilated to expand the stent against the vessel wall and to open the vessel at the lesion position. The expandable stent also deploys and holds this portion of the vessel open. Any embolic debris created during the interventional procedure will be captured and retained by the self-expanding filter distal to the interventional site and will be prevented from traveling to downstream vessels where possible blockage can occur.
After the interventional procedure has been completed and all of the emboli have been trapped by the filter, the expandable member at the lesion site can then be deflated and withdrawn from the vessel. The remaining portion of the self-expanding filter can thereafter be fully deployed against the vessel wall. This deployment of the filter causes the emboli to be trapped between the vessel wall and the self-expanding filter. The physician fully deploys the remaining portion of the expandable filter by retracting the proximal end of the restraining sheath until the expandable filter is fully unsheathed.
Alternatively, the expandable member may be deflated and withdrawn from the vessel after the proximal end of the self-expanding filter has been deployed against the wall of the vessel to trap the emboli.
The self-expanding filter may be made from a self-expanding stent having a strut pattern which provides an adequate filtering media that can safely and effectively trap emboli of a given size. Alternatively, the self-expanding filter may be made from a filtering material which traps the emboli, but permits blood flow there through. Expandable members, such as self-expanding cylindrical rings, could be placed along the length of the filtering material to create a cylindrical shape filter which will be expandable and able to trap embolic debris. Since the self-expanding filter can be made from biocompatible material, the filter may remain permanently implanted within the patient""s vasculature to prevent any trapped emboli from being released into the blood stream.
These and other advantages of the present invention will become more apparent from the following detailed description of the invention, when taken in conjunction with the accompanying exemplary drawings.